This invention relates to a device for indicating the charging state of a battery such as used in a motor vehicle and more particularly to an indicating device capable of indicating an overcharged state of a battery.
From a conventional device of the type to which the invention pertains, it is generally known that when the ignition system of a vehicle is turned on but the combustion engine itself is not started, an indicating lamp is illuminated to indicate a non-charging state of the vehicle's battery and that when the engine is started thereby driving the alternator, the indicating lamp is turned off in accordance with a rise in the output voltage of the alternator so as to indicate a fully charged state of the battery.
If the output voltage of the alternator drops to zero for any reason during operation of the engine, the indicating lamp is illuminated to warn the driver of the non-charging state of the battery. However, if the output voltage of the alternator were to become extremely high due to failure, for example, of a voltage regulator during operation of the engine, the indicating lamp would remain off and the battery would be overcharged. This could result in disastrous damage such as spouting of electrolyte from the battery and destruction of electric loads connected to the battery.